What are some good chiropractic websites where one can study x-ray line drawings?

I'm learning to draw lines on x-rays at a chiropractors office but i want to study at home. Are there any good websites that thoroughly explain how to draw x-ray lines on all sections of the spine? (LL,LC,LD,APP,APD,APC,APOM,FLEX,EST.etc.,) i would greatly appreciate it!!! thanks :)